The present invention relates generally to cameras, and more particularly, to a digital camera having a combined optical zoom and digital zoom feature.
In general, both digital and analog cameras must give feedback to a user of what area of a scene to be photographed will be captured when a picture is taken. This has traditionally been accomplished using a built-in device called an optical viewfinder an optical window that enables the user to visualize the scene and see exactly what area of the scene will be captured by the camera lens system.
In order to change the area to be captured by the camera lens system, many digital and analog cameras also include what is commonly called a zoom feature. The zoom feature is limited to optical zooming in the analog camera but may include both optical zooming and digital zooming in a digital camera.
Before discussing the merits of optical and digital zooming, it may be beneficial to briefly review the difference between what is known in the state of the art as a through the lens (TTL) camera and a point and shoot (PAS) camera.
In the TTL camera, as a user views a scene to be photographed he or she utilizes the camera viewfinder. More particularly, the user is viewing the scene through the lens system of the camera. That is, with the help of an internally positioned mirror within the TTL camera, the light passing through the lens system is reflected by the internal mirror and directed to the optical viewfinder for consideration by the user. When the user is satisfied with the scene to be captured, the mirror is repositioned allowing a direct light path to the photosensitive plane of the camera, and thus, allowing the scene to be captured as viewed through the optical viewfinder.
The PAS camera is much less expensive and does not allow the user to view the scene through the primary lens system. Instead, the optical viewfinder is provided with a secondary lens system that moves in and out in tandem with the primary lens system. In short then, in the PSA camera two separate light paths are established; one light path for the primary lens system to the photosensitive plane of the camera and another light path through the secondary lens system to the viewfinder for the scene preview benefit of the user.
Considering now the merits of the two types of zooming, optical zooming and digital zooming, it will be understood by those skilled in the art that optical zooming is a mechanical operation that affects movement of the primary lens system so as to enlarge or reduce a viewed object. Thus, for example, by moving the primary lens system a user may, in a smooth mechanical transition, view a group arrangement of flowers down to a single flower within the group and then back to the entire arrangement. This transition is commonly called xe2x80x9czooming inxe2x80x9d and xe2x80x9czooming outxe2x80x9d of the scene.
With the advent of digital cameras and photography, two new developments emerged: imaging view display modules, known as liquid crystal display (LCD) units and digital zooming. With the LCD unit, a user is able to independently view the scene both before the image is captured, in a preview mode of operation, and after the image has been captured and stored, in a post-view or review mode of operation. In short then, the preview mode of operation is essentially the same mode of operation found in a TTL type of camera as the image displayed on the LCD is taken directly from the photosensitive plane of the digital camera that is otherwise called a charged couple device (CCD).
Digital zooming is an electrical manipulation that selects a portion of the image converted by the CCD so that the selected portion appears to be enlarged when viewed on the whole viewing area of the LCD. From the foregoing, it will be understood by those skilled in the art that the same effects of optical zooming can be achieved and viewed on the LCD without having to incur the high costs associated with providing a moving primary lens system. The trade off for such a benefit however, is degradation in the image quality as viewed on the LCD as the CCD utilizes fewer pixel locations.
In certain high end digital cameras, the degradation in image quality brought about by digital zooming is overcome by providing a conventional optical zooming feature. In this type of camera, the viewfinder tracks the camera lens to enable the user to visually see the effects of the optical zooming. Alternatively, the user may also view the effects of the optical zooming on the LCD in the preview mode of operation as the magnification is achieved by the primary lens system prior to the object image being converted by the CCD. In most situations however, the user will not utilize the LCD for the purpose of observing optical zooming as LCD use places a high electrical drain on the battery system of the camera.
Recently, certain digital cameras have been offered providing both optical and digital zooming. In such cameras, the user is able to select which one of the effects is desired to arrive at a desired magnification. Thus, for example to arrive at a 4xc3x97-magnification factor a user could select a 2xc3x97 optical effect and a 2xc3x97 digital effect.
While such combined effects are desirable in the preview mode of operation, the combined zooming effect has been less than desirable due to the high electrical drain on the camera battery system. That is as the user gets the xe2x80x9cwhat you see is what you getxe2x80x9d view of image data only by viewing the LCD image there is a constant power drain when the combined zoom effect is in operation.
From the foregoing, it should be understood that when the LCD is powered off, the user is limited to viewing only the optical zooming effects through the viewfinder. In this regard, in prior art digital camera with combined zoom features, the optical zoom is always enabled while the digital zoom is only enabled when the LCD is in a powered up state of operation. In this manner, the user would never be in a situation of guessing at what exactly is included in the scene to be captured.
While the above discussed cameras and methods of operation provide the combined effects of both optical and digital zooming, the effects of the digital zooming significantly reduce the useful operating period of the camera relative to the available battery power source. In other words, with a combined optical and digital zooming feature camera, the costs of operating the camera are significantly higher as expensive batteries must be replaced on a much more frequent basis.
Therefore it would be highly desirable to have a new and improved digital camera that includes both optical and digital zooming features while simultaneously facilitating low battery drainage. Such a new and improved digital camera should also be easy to use always permitting the user to know exactly what scene will be captured for image reproduction purposes whether operating in an optical zoom mode or a digital zoom mode.
In accordance with the present invention, a digital camera includes a zoom features that combines both optical zooming and digital zooming without requiring the use of a liquid crystal display (LCD) unit and thus, facilitates low battery drainage. The new and improved digital camera includes a motor activated primary lens and secondary lens system that operate in tandem over the optical zoom range of the camera. The user views the effects of the optical zoom through a viewfinder that sees the scene to be photographed through the secondary lens system. At the end of the optical zoom range the motor continues to drive the secondary lens system to provide the user with an optical simulation of the digital zoom effects. In short, the user is able to visualize a zoom factor indicative of the product of various optical and digital zoom factors without activation of a LCD unit. In the alternative, the LCD unit may be activated to permit the user to see the combined effects of optical and digital zooming in a preview mode of operation using the LCD unit. In the zoom mode of operation a zoom control algorithm facilitates a process wherein a microprocessor generates electrical signals to control the motor operation to provide the whole of both the optical zoom range and the digital zoom range in accordance with the novel method of using the digital camera.